You can see who did how much damage to specific mobs, especially adds, on boss encounters, by selecting a fight, choosing the creature, Damage by Actor tab, the box at the bottom of the page is "Damage Taken From".

Damage Taken From is a most awesome box of information. In fact it is so awesome it is one of the first things I look at on most logs. There is one thing in my mind that would make it more awesome.

Any chance you could add all the participants of that particular fight, even the 0% folks to the box/chart. It is much more visually impacting to see a 0% and a name.